Delayed diagnosis of pediatric intra-articular epithelioid sarcoma: a case report and literature review

Abstract

Background: Epithelioid sarcoma (ES) is a rare form of mesenchymal malignancy that rarely occurs in children. Only seven cases of intra-articular epithelioid sarcoma have been reported in the medical literature.

Case presentation: In this report, we presented the case of a 13-year-old girl with a delayed diagnosis of ES in the left knee. Her initial diagnosis was mistaken for Pigmented Villonodular Synovitis (PVNS) but ruled out later by the first biopsy. However, the lesion rapidly regrew again after arthroscopy, raising suspicions of malignancy. A comprehensive histochemistry examination was conducted again, leading to the diagnosis of INI-1 negative epithelioid sarcoma. Unfortunately, the girl passed away seven months later due to early metastasis of the tumor.

Conclusion: Careful consideration should be given to the differential diagnosis of pediatric patients presenting with monoarthritis. This report highlights the importance of early and accurate diagnosis and underscores the necessity for effective treatments for epithelioid sarcoma. Surgical resection or radical surgery is recommended, while novel treatment strategies targeting EZH2 show promise.

Keywords: Case report; Epithelioid sarcoma; INI-1; Monoarthritis.

Fig. 1

Clinical features of the case. (A) Clinical view of the right knee joint, obviously swollen compared to left knee joint. (B) Computed Tomography (CT) scan showed multiple small nodules (white arrows) in both lungs in second hospitalization

Fig. 2

The MRI images of the right knee from different positions. (a1-d1) In the first hospitalization, the MRI images showed a large amount of fluid signal shadow in the right knee joint cavity from different positions, including the lateral sagittal position (a1, T1WI; c1 PDWI), the transverse axial position (b1, T2WI) and the coronary position (d1, PDWI). (a2-d2) During the second hospitalization, the MRI images highlighted patchy high signal shadows (white arrows) in the surrounding soft tissues of the right knee (observed in a2, T1WI; b1, T2WI; c2 PDWI; d2 PDWI-COR). A patchy low T1-weighted signal (a2) and high PD-weighted fat-suppressed signal (c2, d2) were seen in the distal metaphysis of the right femur and proximal metaphysis of the tibia, with unclear borders. Fluid signal shadows and strip-like signal shadows were seen within the right knee joint cavity. Abbreviations: T1WI, T-weighted image; T2WI, T2-weighted image; PDWI, proton density-weighted image; PDWI-COR, coronary proton density-weighted image

Fig. 3

The pathologic findings of the ES patient. (A) The biopsy specimen showed epithelial-like cells growing in a streak or patch pattern with vesicular nuclei, prominent nucleoli, atypical cell shape and nuclear division (H&E, 400×). IHC staining showed positive for CK (B, 400×) and negative for INI-1(C, 400×) and ERG (D, 400×)